#pragma once
#include <iostream>
#include <string>

class Timestamp {
    public:
        Timestamp();
        explicit Timestamp(int64_t microSecondsSinceEpoch);
        static Timestamp now(); //属于整个类，没有隐含的this指针
        std::string toString() const;
    private:
        int64_t microSecondsSinceEpoch_;
};